The present invention relates generally to a cab suspension for an over-the-highway truck or tractor vehicle. In particular, the present invention relates to a laterally damped panhard rod cab suspension.
Over-the-highway truck or tractor vehicles include a frame for supporting an operator""s cab. The frame is typically supported by load springs extending between the frame and the axles of the vehicle. Due to the relatively large load that such a vehicle transports, the load springs have a relatively high spring rate. Thus, any uneven road surface that the vehicle is operating over or any imbalance or untrueness of the tire and wheel assemblies of the vehicle results in a shock or vibration that is transmitted to the operator""s cab.
Cab suspensions have been developed which include cab springs and dampers located between the vehicle frame and operator""s cab to minimize transmission of such shock and vibration to the cab. On most conventional heavy trucks, the rear suspension includes air or coil springs and vertical shock absorbers to support the mass of the cab and dampen vertical shock. Existing cab suspensions use a panhard rod or lateral shock absorbers to control lateral movement of the cab with respect to the frame.
Panhard rods are used heavy trucks that have day cabs. Sleeper cabs are typically heavier than day cabs. As a result, use of a panhard rod in a sleeper cab suspension may not result in an acceptable level of comfort for the driver and passenger due to the greater mass of the sleeper cab trying to laterally move.
Lateral shocks are used in sleeper cabs to soften the lateral inputs into the cab. The lateral shock absorbers are mounted to the cab and frame with brackets. The lateral shocks and mounting brackets are heavier and more expensive than a panhard rod.
There is a need for a cab suspension for heavy trucks that includes a laterally damped panhard rod.
The present invention concerns a laterally damped panhard rod for use in a cab suspension of an over the highway truck or tractor. The laterally damped panhard rod assembly includes a torsion spring and a panhard rod. The torsion spring is connected to a frame of the vehicle or the cab. A first end of the panhard rod is connected to the torsion spring. The second end of the panhard rod is connected to the vehicle frame or cab that does not mount the torsion spring. The panhard rod and torsion spring assembly biases the cab toward a centered position relative to the frame and damps lateral movement of the cab with respect to the frame.
In one embodiment, the panhard rod and torsion spring assembly is used in a suspension for a cab of an over the highway truck or tractor having a frame. The frame includes a pair of spaced apart frame rails and a transverse member that interconnects the rails. The suspension includes first and second spaced apart springs that are interposed between and connected to the cab and to the transverse member for modulating relative motion of the cab with respect to the frame. A pair of spaced apart motion dampers are interposed between and connected to the cab and transverse frame member. The motion dampers interconnect the cab and the frame to damp relative cab and frame movement both toward and away from one another. The torsion spring is connected to the transverse member of the frame or the cab. The first end of the panhard rod is connected to the torsion spring. The second end of the panhard rod is connected to the other of the transverse member of the frame and the cab. In one embodiment, the suspension that includes a panhard rod and torsion spring assembly is used in a suspension of a sleeper cab.
When installed in a cab suspension of an over the highway truck or tractor, the panhard rod and torsion spring biases the cab toward a centered position relative to the frame. The panhard rod and torsion spring assembly maintains the cab in the centered position when inputs to the frame are below a threshold value. The torsion spring allows lateral movement of the cab from the centered position when inputs to the frame exceed the threshold value. The torsion spring damps relative lateral movement between the cab and the frame.
Additional features of the invention will become apparent and a fuller understanding will be obtained by reading the following detailed description in connection with the accompanying drawings.